Which 270x would you be looking at exactly? there is a Sapphire toxic 270x which is supposedly the fastest 270 you can buy and if it is anything like the toxic 280x it'll be a dream for overclocking. Do you have an approximate amount you'd like to spend on a GPU as well? You might be able to strike lucky and pick up a much faster card (e.g. 680) for the money if you shop around.